Abstract

The Newporte field is located just south of the United States-Canada border in Renville County, North Dakota, in the north-central portion of the Williston Basin. Integration of seismic, well-log, and core data supports the interpretation of an impact origin for the Newporte structure. The structure involves both Precambrian basement and lower Paleozoic sedimentary units. Oil and gas production began in 1977 from brecciated basement rocks along the rim of the 3.2-km-diameter circular structure. Both well logs and seismic data were used to determine thickness changes of sedimentary units overlying the structure. Resulting isopach maps reveal a circular, bowl-shaped feature with a recognizable rim. Microscopic shock metamorphic features in quartz and feldspar are visible in basement clasts that form a mixed breccia with Cambrian Deadwood sandstone within the western rim of the structure. A Late Cambrian-Early Ordovician age is suggested for the structure because of the presence of flat-lying Deadwood sandstone overlying mixed basement/sandstone breccia along portions of the rim. Identification of the Newporte structure as an impact crater adds to the growing base of evidence revealing the relevance of impact craters to petroleum exploration.

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